C08G75/00—Macromolecular compounds obtained by reactions forming a linkage containing sulfur with or without nitrogen, oxygen, or carbon in the main chain of the macromolecule

C08G75/02—Polythioethers

C—CHEMISTRY; METALLURGY

C07—ORGANIC CHEMISTRY

C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS

C07C2601/00—Systems containing only non-condensed rings

C07C2601/12—Systems containing only non-condensed rings with a six-membered ring

C07C2601/14—The ring being saturated

C—CHEMISTRY; METALLURGY

C07—ORGANIC CHEMISTRY

C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS

C07C2601/00—Systems containing only non-condensed rings

C07C2601/18—Systems containing only non-condensed rings with a ring being at least seven-membered

C07C2601/20—Systems containing only non-condensed rings with a ring being at least seven-membered the ring being twelve-membered

Abstract

Polythiols having more than two terminal and/or pendant thiol groups per polymer molecule are formed by the free radical catalyzed addition of a monomer system made up of either hydrogen sulfide or a dithiol alone or in combination with an acetylenic compound to a polyolefin having at least three olefin sites. The polyolefin is preferably a triterminal olefin. The polythiol products are liquid, essentially gel-free materials having number average molecular weights varying from 200 to 30,000. The polyfunctional prepolymers of the invention can be cured to stable three-dimensional networks with inexpensive bi-functional oxidants such as lead dioxide. Additionally, prepolymer compositions having 3 or more pendant or terminal thiol groups per molecule when combined with polyfunctional organic reagents, such as diepoxides, form stable, high-tenacity adhesive systems.

Primary Examiner- Donald E. Czaja Assistant Examiner-M. 1. Marquis Attorneys-Chasan and Sinnock and J. E. Luecke ABSTRACT: Polythiols having more than two terminal and/or pendant thiol groups per polymer molecule are formed by the free radical catalyzed addition of a monomer system made up of either hydrogen sulfide or a dithiol alone or in combination with an acetylenic compound to a polyolefin having at least three olefin sites. The polyolefin is preferably a triterminal olefin. The polythiol products are liquid, essentially gel-free materials having number average molecular weights varying from 200 to 30,000. The polyfunctional prepolymers of the invention can be cured to stable three-dimensional networks with inexpensive bi-functional oxidants such as lead dioxide. Additionally, prepolymer compositions having 3 or more pendant or terminal thiol groups per molecule when combined with polyfunctional organic reagents, such as diepoxides, form stable, high-tenacity adhesive systems.

ll 2 SYNTHESIS OF POLYTHIOL POLYMER groups per molecule (hereafter referred to as available thiol INTERMEDIATES FROM POLYUNSATURATIED sites) can be formed by the free radical addition of a monomer HYDROCARBONS system composed of either hydrogen sulfide or a dithiol, alone or in combination with an acetylenic compound, to a FIELD OF THEINVENTIQN 5 polyolefin having at least three olefin sites, preferably three terminally located sites of unsaturation. With the present system, it is possible to prepare polymers having wide variations in the number of thiol functions per polymer molecule in a given molecular weight range by controlling the amount of polyolefin used. By controlling the: amount of polyolefin comonomer in the feed, it is theoretically possible to form polymers in any given molecular weight range with a functionality varying between more than two terminally or pen dantly located thiol groups and the theoretical gel point of the polymer. The polythiol polymers of the invention exhibit number average molecular weights varying from about 200 to DESCRIPTION OFTHE PRIOR ART 30,000. Liquid polymers which find. the greatest utility in mastic and adhesive applications have number average The addition of dithiols (dimercaptans) to unsaturated molecular weights varying from about 1,000 to about 8,000. hydrocarbons has been known for some time. For example, One class of polythiols is formed. by the reaction of a Marvel and chambers, J. Am. Chem. Soc. 70, 993 (l948)and polyolefin with H 8, a dithiol, or mixtures thereof in ac- Marvel and Cripps, J. Pol. Sci. 8, 313 (1952) reportedthe cordance with thefollowing equation:

The present invention relates to novel, low molecular weight polythiol prepolymers, a novel free radical addition process for their formation and to cured compositions formed from said polymers. More particularly, the present invention is 10 directed to low molecular weight polythiols formed by the addition of a monomer system made up of either hydrogen sulfide or a dithiol, alone or in combination with an acetylenic compound to a polyolefin having at least three olefinic sites of unsaturation. l

Q+ CX=GYZ H(SRi)sSH (OYZ=CX Q{-CHX'CYZ(SRr)a-SH] a a n-d reaction of dithiols with conjugated W and V wherein Q is a polyvalent organic radical, R, is a divalent ordiolefins. The polymeric compositions so produced were esganic radical, preferably an alkylene radical, having from one sentially straight-chain materials of relatively low molecular to carbon atoms; X, Y and Z are either a hydrogen radical weight having an average of from one to two terminal thiol 30 or a monovalent organic radical, in particularan alkyl radical, functions er olymer mole ule, Simila ly, i copending lihaving from one to 30 carbon atoms; a varies from three to 30; cation Ser. No. 541,696, filed Apr. 1 l, 1966, the formation of b ranges from 287010 and d Varies from Zero to 2 essentially straight-chain polythioethers by the addition reae- Polyolefins having terminal vinyl groups are particularly attion of dithiols ith acetylenic compounds i rcporteti S h tractive feedstocks in polythiol formation. Their use is demonpolythioether addition products have a maximum of two terrated llllhe following equatlonl minal thiol substituents per polymer molecule. Because the polythioether polymers of the prior art had a maximum of two terminal and/or pendant thiol functions per polymer z L( 3 (311:932] mH(S R1)bSH molecule, these materials could be cross-linked to stable m three-dimensional networks only with the use of relatively exr Pensive Polyfunctional reagents. Inexpensive bifunctional cur- F CHzCH2 sRl bSH1 ing agents, such as lead dioxide, could not be used as such re- H m a ents; the mere] served to extend the l mer chains and t fa iled to fot m a stable, rubber three-dimen iorfal network. gg l is kl f s: giz figz 321:;

, car on a oms; 3 IS a rva en y c preferably an alkylene radical, having from one to 10 carbon SUMMARY OF THE INVEN'HON atoms; R and b are as defined above;fis zero or one; and m varies from three to 10. Now, in accordance with the present invention, it has been Representative, nonlimiting reactions and products contemfound that polythiol polymer intermediates having on the plated by this invention may be represented by the following average at least two terminally or pendantly located thiol eq at o L\ (III) (W omomsn 'sno] x (VII) or (VIII) 74 While all of the above equations illustrate reactions involving triterminal olefins, it should be recognized that other types of polyolefins having at least three olefin sites can also be used. Equation (a) demonstrates the reaction of a triterminal olefin with hydrogen sulfide. The relative proportions of the amounts of products I, II, III IV, etc. obtained with the reaction of hydrogen sulfide with triolefin is strongly dependent upon the molar ratio of the reactants present in the reaction zone. A very high excess of the hydrogen sulfide results in the formation of low molecular weight trithiol (I) and tctrathiol (II). A small excess of H 8 usually leads to higher molecular weight polythiols and eventually cross-linked products.

Equation (b) illustrates the reaction of a triterminal olefin with a dithiol. If a large excess of dithiol is used in the reaction, such as greater than 2 moles of dithiol per mole of olefin unsaturation, the predominant product obtained is a trithiol (V). If smaller amounts of dithiol are used in combination with the triterminal olefin again high molecular weight polythiols are formed in the case of high reactant conversion. If R is a divalent hydrocarbon radical having an excess of 12 carbon atoms or if the thiol group of the dithiol is attached to a secon dary carbon atom, the reaction proceeds at a much slower rate.

Equation (c) illustrates a coaddition reaction of a triterminal olefin with an acetylenic compound and a dithiol. Again, whether or not products VII and VIII are obtained in substantial yield is dependent upon whether the molar ratio of dithiol to triterminal olefin in the reaction zone is maintained at levels above or below about 2 moles of dithiol per mole of olefin unsaturation present in the reaction zone. The relative molar amounts of acetylenic compound to dithiol compound present in the reaction zone determines the number of repeat units in the polythioether (the value of n) and whether or not the polymer will contain terminal olefin or thiol functionality. If the acetylenic compound is present in the reaction zone in excess of the dithiol, the product recovered will contain high levels of terminal olefin functionality. In contrast, if the dithiol is in excess of the acetylenic compound present in the reaction zone, the final product secured will contain predominantly thiol terminal functionality.

Products VII and VIII can also be obtained utilizing sequential reaction techniques as opposed to the coaddition reaction illustrated in equation (c). For example, the triterminal olefin can be reacted with a large excess of dithiol to form a thiol-terminated product. This product can be isolated from the reaction mixture and contacted with a molar excess of the acetylenic compound to form a polythioether product having terminal olefin functionality. This product in turn can also be isolated from the reaction mixture and contacted with an excess molar amount of dithiol to form products whose terminal functionality is primarily composed of thiol groups. Such sequential reactions can be continued until products having the desired molecular weight and terminal or pendant functionality are secured.

Product II of equation (a) and product VI of equation (b), because of their high levels of available thiol sites, find particular utility in adhesive applications. Products II and VI, when mixed with cross-linking agents such as diepoxides and polyepoxides form excellent adhesive systems that rapidly cure at room temperature conditions. The products of equation (c), especially product VII, find their greatest utility as the base substituent of mastic compositions. Such materials can be readily cross-linked with diisocyanates, diacrylates, dimaleates, divinyl sulfone, etc. to stable, three-dimensional networks. They can also be cured utilizing inexpensive oxidative curing systems. The value of n as used in products VII and VIII of equation (0) can vary over a wide range. Generally, n ranges between one and 100, preferably between two and 30. Products finding the greatest utility as the liquid base constituent for mastic compositions exhibit n values varying from about three to [5.

The products of this invention, depending upon their molecular weight, are essentially colorless liquids of varying viscosity or low melting solids. Polythioetherpolythiol products which have more than three terminally or pendantly located thiol functions per molecule and which find the greatest utility in adhesive applications exhibit number average molecular weights, as determined by vapor pressure osmometry, varying from 400 to 20,000, preferably 500 to 15,000. Products having the greatest utility as the base constituent of mastic compositions and which usually have on the average of more than two to three terminally or pendantly located thiol functions per polymer molecule exhibit number average molecular weights, as determined by vapor pressure osmometry, varying from about 800 to 10,000, preferably between 1,000 and 8,000.

The polyolefin utilized as a starting material in the formation of the polymer products of this invention is a polyolefin compound having at least three olefinic sites of unsaturation. Useful polyolefins may have from seven to carbon atoms, preferably eight to 36 carbon atoms, and the olefinic sites of unsaturation may be either conjugated or nonconjugated and can be located either terminally or internally in the polyolefin molecule. As terminal sites of unsaturation are more reactive than internally located olefin sites, it is desirable that the polyolefin utilized as a starting material have at least two terminally located sites of unsaturation. Most preferably, the

polyolefin used is a triterminal olefin having the general formula:

wherein R is a trivalent organic radical, particularly a trivalent hydrocarbon radical, having from one to 30, preferably one to 12, carbon atoms; R is a divalent radical, preferably an alkylene radical having one to 10 carbon atoms; and x is zero or one.

As stated previously, the present polythioetherpolythiol compositions are formed by reacting relatively minor amounts of polyolefins with a monomer system made up of either hydrogen sulfide or dithiol compound alone or in combination with an acetylenic compound. Useful dithiol compounds have the general formula:

Particularly preferred thiols are those compositions wherein R" is a lower alkylene radical such as an alkylene radical having from two to four carbon atoms as such materials are especially reactive and are readily available at relatively low cost.

Acetylenic compounds are used as the third component in some of the polymer systems of this invention. Applicable acetylenic compounds have the general formula:

CHECR wherein R is a hydrogen radical or a C C; hydrocarbon radical. Preferably, R' is (l) a hydrogen radical; (2) a C, 5 C alkyl group e.g. methyl, ethyl, pentyl, etc.; (3) a C -C alkenyl radical such as vinyl, allyl, 3-butenyl, etc.; (4) a C C alkynyl radical, e.g. ethynyl, 4-pentynyl; (5) a C,-C, aralkyl radical such as benzyl, phenylethyl, naphthyl methyl; and (6) a C,--C hydroxyalkyl radical such as hydroxymethyl. Although any of the above-named materials will incorporate into a polymer system made of a polyolefin and either hydrogen sulfide or a dithiol, it is especially preferred that R' be a C radical or lower, especially a C,-C alkyl radical. Although monosubstituted acetylenes are preferred for use in the instant invention, acetylene itself and disubstituted acetylenic compounds having the general formula:

RIIICECRIII can also be used either alone or in combination with monosubstituted acetylenic compounds.

A preferred reactant combination is a bis-primary dithiol compound together with trivinyl cyclohexane and methylacetylene. Such a combination leads to a mixture of polythioether dithiols and trithiols as illustrated by the following equations:

than that of methylacetylene, and acetylenes in general with dithiols. Consequently, the above trithiol adduct is formed before significant amounts of the acetylene react with the dithiols. Of course this adduct may also be prepared separately in the absence of the acetylene compound.

The trithiol adduct is then reacted with the acetylene and the excess dithiol in an alternating fashion so as to provide a trifunctional polythioether:

L HS C Hg) mSH (CH )mSCH=CIJH (CHDm s H} n+1 a Polythloether trithiol Concurrent with the above reactions some of the dithiol reacts with methyl acetylene without any trithiol being involved. This leads to difunctional polythioethers:

Of course, tetrathiols, pentathiols, etc. that are formed via the reaction of trivinyl cyclohexane with dithiols will also react in the same manner and lead to the corresponding polythioether polythiols.

According to the process of this invention, a polyolefin having at least three olefinic sites of unsaturation is reacted with a monomer system made up of either 1 hydrogen sulfide, (2) a dithiol, (3) hydrogen sulfide and an acetylenic compound, or (4) a dithiol and an acetylenic compound. The ratio of the reactants present in the reaction zone has a strong effect upon the molecular weight of the polymer products and the extent to which the products contain either terminally or pendantly located thiol functionality. in two component systems involving the reaction of either hydrogen sulfide or a dithiol with a polyolefin, at least I mole of either hydrogen sulfide or dithiol should be present in the reaction zone for every mole of olefinic unsaturation present in the reaction zone. It is preferred, however, that at least from three to times the minimum amount of either hydrogen sulfide or dithiol be present during the addition reactions.

If products having more than two terminal or pendantly situated thiol functions are to be obtained from two com-. ponent reactions at least 1 mole of H,S or dithiol should be present in the reaction zone for every mole of unsaturation present in the acetylenic compound and polyolefin. Preferably, from two to 10 times the minimum amount of H 8 or dithiol is present in the reaction zone. In the three component reactions, the maximum amount of polyolefin desirably present in the reaction zone varies from 0.1 to 10 mole percent of the total reactants. If the polyolefin is present in excess of these levels, the polymer composition obtained at high reactant conversions may be severely gelled.

The process for the production of the polythioetherpolythiol addition products can be carried out in bulk, in the presence of inert solvents, or with the use of water emulsion techniques. Both two and three component reactions can be carried out most efficiently using bulk polymerization techniques, that is, carrying out the addition reaction in the absence of solvents. When higher molecular weight polythioetherpolythiols are desired, the reaction is preferably carried out in the presence of an inert solvent or in a typical water-surfactant emulsion system. When the addition reaction is conducted in the presence of a solvent, the reaction monomers make up from 10 to 95, preferably to weight percent of the total monomer-solvent system.

The conditions at which the addition reactions are conducted can vary over a wide range. High yields of polythiols can be obtained for addition reactions carried out in bulk or in solvents at temperatures varying from about l00 to 0, preferably 80 to 80 C., in from 5 minutes to 12 hours, 70 preferably 10 minutes to 6 hours. When emulsion techniques are utilized, the addition reaction should be conducted at temperatures varying from l5 to 50 C. for from 5 minutes to 4 hours.

The addition reactions are not critically sensitive to pres- 75 sure. However, the pressure within the reaction zone should be sufficient to maintain the major portion of reactants in the liquid state at the temperature used for the reaction. In general, pressures varying from 1 to l0 atmospheres, preferably atmospheric pressure, can be used. The gaseous acetylenic compound may be gradually introduced during the reaction. In reaction systems wherein potentially explosive acetylenic compounds are used, it is often desirable to pressurize the reactor with an inert gas such as nitrogen in order to maintain the reaction monomers in the liquid state.

While the instant addition reactions will proceed merely by heating the reagents, it is desirable to employ a free radical initiator to promote the formation of the desired products. Radiation such as ultraviolet light or gamma-radiation alone or in conjunction with the application of heat may be used to promote the addition reactions. For example, a C0 gamma irradiation source emitting 4,000 curies may be placed at a 6- centimeter distance from a 2 -liter reactor to initiate a polyaddition to effective completion in 4 hours.

Additionally chemical free radical initiators such as organic peroxides, preferably alkyl peroxides, azo compounds, etc. may be used instead of radiation or in combination with it. Representative examples of useful chemical initiators include p-butyl hydroperoxide, bis-t-butyl peroxide, (azo-bis-isobutyronitrile), etc. Generally, only minor quantities of the chemical initiators are necessary to promote the addition reactions. Normally, between 0.05 and 10 mole percent, preferably between 0.1 and 5 mole percent, of chemical initiator is used based upon the number of moles of reactant monomers present in the reaction zone.

The reaction vessel used for the addition reactions contemplated by the invention may be constructed of any material that is inert to the reactants and catalysts used and is further capable of withstanding the operating pressures. Reaction vessels formed of quartz, stainless steel, or glass-lined steel are satisfactory.

Although the polythiol and polythioetherpolythiol products formed with the process of this invention have many uses as intermediates because of the terminally or pendantly located thiol and olefinic functionality present within the polymer molecule, materials having on the average of three or more available thiol sites per polymer molecule find particular utility in adhesive applications. Polythioetherpolythiols and polythiols having on the average of two or more than two terminally or pendantly located thiol functions per polymer molecule can be used as the base substituent for mastic compositions.

In adhesive applications the polythioetherpolythiols can be advantageously used in combination with polyepoxides and diepoxides. For example, polyether A,

or polyglycidyl ethers.

may be used. Trialkylamine compounds serve well as curing catalysts for such combinations. In the presence of catalysts curing usually takes place at room temperature. Curing may be accelerated by heating at temperatures up to C. The polythiol components of such adhesive compositions act as internal flexibilizers. The compositions display excellent adhesion on aluminum, steel, copper, wood, glass, ceramics, plastics, etc.

As stated previously, the polythiol products of this invention having more than two pendantly or terminally located thiol functions per polymer molecule can be readily cross-linked to stable, rubbery three-dimensional networks using inexpensive oxidative curing systems. For example, lead dioxide, zinc peroxide, calcium peroxide may be used as oxidizing agents. Such curing compositions may also contain a curing retarder usually stearic acid. Curing takes place at room temperature in a period ranging from a few hours to several days. Heating of the mixture accelerates curing. Reaction with difunctional reagents such diisocyanates, diepoxides, diacrylates, dimaleates and divinyl sulfone will also result in desirable cured networks.

Prior to curing operations in both adhesives and mastics applications, the polythiol and polythioetherpolythiol products may be compounded with stabilizers, plasticizers, or extender oils and various types of fillers. Up to 200 parts of carbon black, finely divided petroleum coke, or other noncarbon fillers such as titanium oxide, magnesium oxide, silica, etc., may be compounded with 100 parts of the product. The cured mastic compositions are highly resistant to ozone and oxygen degradation and to attack by organic solvents, and organic and inorganic acids and bases. Hence, the cured materials find particular utility in automotive applications.

The invention will be further understood by reference to the following examples.

(CH3CHISH)Z Tetrathlol v A mixture of 32.4 grams (0.2 moles) of isomeric 1,2,3-, 1,2,4-, and 1,3,5-trivinyl cyclohexanes, containing mainly the 1,2,4-isomer, was placed in a quartz pressure tube equipped with a magnetic stirrer and a Teflon screw value. The tube was evacuated and 109 grams (3.2 moles) of hydrogen sulfide was condensed in the tube with the triolefin. The tube was then closed, stirring commenced and the reactants radiated with a 75-watt l-lanau ultraviolet immersion lamp having a high-pressure, wide-spectrum mercury arc. Radiation was continued for 24 hours during which time the reactants were maintained at a temperature of about 16 C. Following completion of the reaction period, excess hydrogen sulfide was vented from the tube and the product distilled at 100 C. at pressure of about 0.25 millimeters of mercury. The distillation residue consisted of 48 grams of a colorless liquid product. This product was then heated to 170 C. at a pressure of about 1.5 l millimeters netic resonance (NMR) spectrum of this overhead fraction exhibited the ratio of olefinic versus total hydrogen characteristics of the monoadduct shown in the reaction scheme. The nuclear magnetic resonance spectrum of the residue indicated that no vinylic protons were present. The number average molecular weight of the second distillation residue as determined by vapor pressure osmometry at 37 C. in a benzene solution containing 2.4 weight percent residue was 471.

From the nuclear magnetic resonance spectrum and molecular weight evidence, the residual product of the second distillation was believed to have the structural formula of the tetrathiol given in the reaction scheme. The calculated composition of the tetrathiol is 58.24 weight percent carbon, 9.36 weight percent hydrogen, and 32.4 weight percent sulfur. An elemental analysis of the residue of the second distillation indicated that the composition consisted of 58.79 weight percent carbon, 9.40 weight percent hydrogen and 31.81 weight percent sulfur. The calculated number of thiol groups per molecule for the tetrathiol is of course four. The found number of thiol groups per molecule, i.e. thiol functionality by the Zerewitinoff method for the residue was 3.9. Therefore the major component of the residual polythiol is assumed to be the tetrathiol although minor quantities of the other thiolic products indicated in the reaction scheme may be also present.

EXAMPLE 2 Addition of Excess Tetramethylenedithiol to Trivinylcyclohexane A stirred mixture of 16.2 grams (0.1 mole) of trivinylcyclohexane and 73.2 grams (0.6 mole) tetramethylenedithiol was irradiated with an ultraviolet lamp at 16 C. for 24 hours. The unreacted tetramethylenedithiol was removed via distillation by heating the crude product at C. at 0.1 millimeters of mercury pressure for 2 hours. The colorless, liquid residual product weighed 50.5 grams, which corresponds to a 95.5 per cent yield calculated for the trithiol of the reaction scheme. The number average molecular weight of the product, as determined by osmometry, was 728. The calculated value for the trithiol is 528. Thiol functionality determination gave a value of 3.1. This data indicates that the major reaction product is the trithiol while a minor amount of tetrathiol is also present.

EXAMPLE 3 Addition of Excess Ethanedithiol to Trivinylcyclohexane To 235 grams (2.4 moles) of 1,2-ethanedithiol was added 64.8 grams (04 moles) of trivinylcyclohexane. The mixture was irradiated at C. for 6 hours with ultraviolet light as described in the previous examples. The excess ethanedithiol and other volatiles were then removed from the resulting mixture by heating it at 140 C. and 0.2 millimeters of mercury pressure. The residual product weighed 153 grams (86 percent yield of the calculated amount for the tetrathiol). A thiol functionality determination gave a value of 4.1 (Zerewitinoff method). The found molecular weight of the product was 897. The calculated molecular weight for the tetrathiol is 795. The higher than theoretical molecular weight is apparently due to the presence of minor amounts of pentathiol.

EXAMPLE 4 Addition of Excess Trimethylenedithiol to Trivinylcyclohexane 12 EXAMPLE 6 Dlthlol CH Trlthlol Following the procedure of example 2 a stirred mixture of 81 grams (0.5 moles) of isomeric trivinylcyclohexanes and 162 grams (1.5 moles) of trimethylenedithiol was irradiated with the Hanau immersion lamp at 16 C. for 6 hours. Following the completion of the reaction period, the unreacted starting materials were removed from the reaction zone by heating the crude product at 140 C. at a pressure of about 0.1 millimeter of mercury. About 190 grams of a colorless liquid was obtained as a residual product. The NMR spectrum of this product indicated that it was substantially free of unsaturation. The number average molecular weight of the products as determined by vapor pressure osmometry at 37 C. in benzene diluent at a polymer concentration of 1.2 grams per 100 cc. was 1,208. On the basis of the NMR and molecular weight data, the product was believed to have the pentathiol structure given in the reaction scheme. The calculated molecular weight for the pentathiol is 1,244. The thiol functionality of the residual product was found to be 4.4.

A mixture of 24.3 grams (0.15 mole) of cyclododecatriene and 97.2 grams (0.9 mole) of trimethylenedithiol was reacted for 24 hours under the conditions of example 3. After the removal of the excess trimethylenedithiol by distillation in vacuo 68 grams of liquid residual product was obtained. This corresponds to a 93 percent yield of the trithiol based on the above reaction. The thiol functionality of the product was 2.8. The molecular weight of the product was found to be 486 while the calculated molecular weight for the trithiol is 557.

A mixture of 4 grams (0.03 mole) of trivinyl-cyclohexane, 40.2 grams (1.005 moles) of methylacetylene and 108 grams (1 mole) trimethylenedithiol was irradiated with ultraviolet light in a quartz pressure tube at 16 C. for 4 hours. The mixture was thoroughly mixed every half hour by shaking. By the end of the 4 hours reaction period a very viscous but homogeneous, clear, colorless liquid reaction mixture was obtained. One hundred and seventeen grams of the crude product were heated at 150 C. under 0.7 millimeters of mercury pressure to remove all the volatile compounds. The residual product weighed 1 10 grams and was unchanged in appearance. An NMR analysis of the distillate showed that it was free from significant quantities of trivinyl-cyclohexane. Then NMR spectrum of the product did not show any vinylic proton signals indicating the absence of any significant unsaturation. An osmometric molecular weight determination gave a value of 2,670. Thiol functionality by the Zerewitinoff method was 2.3 indicating that the product was a mixture of polythioether trithiol and dithiol as shown by the above reaction scheme.

EXAMPLE 7 Coreaction of Trimethylenedithiol Trivinyl-Cyclohexane and Methylacetylene at Atmospheric Pressure with Gamma Ray lnitiation An airtight reactor equipped with an effective, high-speed stirrer, a dropping funnel and a filtered glass gas inductor was charged with 324 grams (3 moles) of trimethylenedithiol under nitrogen. Then 12.2 grams (0.075 mole) of trivinylcyclohexane was added with stirring dropwise over a 1-hour period to the stirred dithiol. During the addition, the mixture was subjected to gamma irradiation from a 4,500 Curie intensity Co source positioned 7 centimeters from the reactor. Thereafter the reactor was evacuated and filled with methylacetylene by introducing the same under the surface of the liquid mixture. Irradiation was continued during the period of methylacetylene addition. The feeding of methylacetylene into the stirred and irradiated mixture was continued at a sufficient rate to maintain atmospheric pressure within the reactor at 35-40C. In this manner 107 grams (2.7 moles) of methylacetylene was added to the reaction mixture in 200 minutes. To complete the reaction, the mixture was irradiated for an additional minutes after the completion of the addition of the methylacetylene. The resulting colorless, viscous polymer was stripped at 0.2 millimeter of mercury pressure with nitrogen at 125 C. for 3 hours. Stripping removed 1.5 weight percent of the crude product as a distillate. NMR analysis showed that the residue was a mixture of the expected polythioether dithiol and trithiol. The osmometric molecular weight of the product was found to be 2,5 70. Its thiol functionality was 2.4

EXAMPLE 8'' EXAMPLE 9 Addition of Excess Ethanedithiol to Triallyl Carbinol To 56.4 grams (0.6 mole) of ethanedithiol was added dropwise with stirring 15.2 grams (0.1 mole) of triallyl carbinol. The addition was completed in 30 minutes. During addition, the mixture was maintained at 15 C. and was irradiated with a ultraviolet lamp. An additional hour of irradiation after completion of the addition resulted in the essential complete reaction of the triallyl compound. After a total of 10 hours of irradiation the excess dithiol was removed by heating the mixture to 90 C. at 0.1 millimeter of mercury pressure. The residual product consisted of 40 grams of a colorless liquid. This corresponds to a 92 percent yield of the trithiol adduct as shown by the reaction scheme.

EXAMPLE 10 Coreaction of Triallyl Carbinol and Methylacetylene with Ethanedithiol EXAMPLE 1 l Coreaction of Trimethylolpropane Methylacetylene with lEthanedithiol Triacrylate and A mixture of 15.5 grams (0.05 mole) of trimethylolpropane triacrylate, grams (0.5 mole) of methylacetylene and 51.7 grams (0.55 mole) of ethanedithiol was reacted as described in example 2 for 6 hours to yield 74 grams (85 percent) of a residual product consisting of the expected mixture of polythioether dithiol and trithiol.

EXAMPLE 12 Oxidative Curing of Polythioethers Having a Thiol Functionality Greater Than 2 The tetrathiol product of example 4 and the diand trithiol mixture of example 5 were compounded with an oxidative 0 curing composition containing 50 percent of lead dioxide as an oxidizer. The composition also contained 5 percent stearic acid as a retarder and 45 percent dibutylphthalate as a plasticizer. Carbon black (Thermax brand) was also added as a filler. Each of the mixtures contained 5 grams of prepolymer, 2 grams of curing composition, and 2.5 grams carbon black. The mixtures were cured at room temperature in a desiccator containing a saturated aqueous solution of potassium thiocyanate. It was observed that tetrathiol was cured to a rubbery composition within 12 hours. The complete curing of the dithiol-trithiol mixture took 36 hours. The latter network showed a higher elongation than the one derived from the tetrathiol. The curing of both residual products could be accelerated by heating.

| CHSN(CHS)I CH; QJJH One part by weight of each of the polythiols derived from the experiments described in examples 1, 3 and 4 was mixed with two parts by weight of the diepoxide cross-linking agent, Bis-phenol A di-glycidyl ether, and 0.1 part by weight of the tertiary amine curing catalyst His-2,4,6- dimethylaminomethyl-phenol. An exothermic reaction started on mixing. The mixtures were applied to stainless steel strips. Two strips were used for each adhesive composition. The strips were overlapped with the area of overlap being 0.5 square inch.

After three days the strips were pulled apart at a rate of 0.05 inch per second. The maximum shear force was determined by the shear lap test (ASTM D4002). The results are tabulated below:

The data show that the polythiols of this invention are cured by the diepoxide at room temperature to give good steel to steel adhesion. Polythioether polythiols of increasing molecular weight display better adhesion but slower cure.

The polythiol-diepoxide compositions were also found to show good adhesion to wood, aluminum, Plexiglas and glass. As such they are useful as general adhesives.

Having thus described the general nature and specific embodiments of the present invention, the true scope of the invention is now pointed out by the appended claims.

What is claimed is:

1. A process for the formation of polythiols which comprises reacting an acetylenic compound and a sulfur compound selected from the group consisting of H,S and hydrocarbon dithiol with about 0.1 to about 10 mole percent of a polyolefin compound having about seven to about 100 carbon atoms and at least three terminal olefinic groups at a temperature of about l00 to 150 C. in the presence of a free radical initiator for a time sufficient to obtain a polythiol product having at least two available thiol sites.

2. The process of claim 1 wherein said hydrocarbon dithiol is a compound having the general fonnula:

wherein R" is selected from the group consisting of (a) a C to C divalent saturated alkylene radical; (b) a C, to C divalent unsaturated alkylene radical; (c) a C to C bis-alkylene substituted aromatic radical; (d) a C to C divalent aromatic radical; and (e) a C to C divalent organic radical containing at least one element selected from the group consisting of sulfur, oxygen and silicon in addition to carbon and hydrogen atoms.

3. The process of claim 2 wherein the said acetylenic compound has a general formula selected from the group consisting ofCHECR and R' CECR' wherein R' is selected from the group consisting of (a) a hydrogen radical; (b) a C to C alkyl radical; (c) a C to C alkenyl radical; (d) a C to C alkynyl radical; (e) a C-, to C aralkyl radical; and (f) a C to C hydroxyalkyl radical.

4. The process of claim 3, wherein at least about I mole of the dithiol and hydrogen sulfide components of the monomer system is employed per mole of olefin unsaturation present in the reaction zone.

5. The process of claim 3 wherein said polyolefin is a tri-terminal olefin having the general formula:

wherein R is a trivalent hydrocarbon radical having from one to 30 carbon atoms, R is a divalent radical having from one to 10 carbon atoms, and x varies from 0 to l.

6. The process of claim 5 wherein R is a trivalent hydrocarbon radical having from one to 12 carbon atoms and x is 0.

7. The process of claim 6 wherein R" is a alkylene radical having from one to four carbon atoms and R' is a C to C alkyl radical.

8. The process of claim 4 wherein said polyolefin is a trivinyl-cyclohexane, R" is an alkylene radical having from two to four carbon atoms and said acetylenic compound is methylacetylene.

Claims (7)

2. The process of claim 1 wherein said hydrocarbon dithiol is a compound having the general formula: HSR'''' SH wherein R'''' is selected from the group consisting of (a) a C1 to C30 divalent saturated alkylene radical; (b) a C2 to C30 divalent unsaturated alkylene radical; (c) a C8 to C30 bis-alkylene substituted aromatic radical; (d) a C6 to C30 divalent aromatic radical; and (e) a C2 to C30 divalent organic radical containing at least one element selected from the group consisting of sulfur, oxygen and silicon in addition to carbon and hydrogen atoms.

3. The process of claim 2 wherein the said acetylenic compound has a general formula selected from the group consisting of CH '''''' and '''' '' C '''' '' wherein R'''''' is selected from the group consisting of (a) a hydrogen radical; (b) a C1 to C30 alkyl radical; (c) a C2 to C20 alkenyl radical; (d) a C2 to C30 alkynyl radical; (e) a C7 to C20 aralkyl radical; and (f) a C1 to C3 hydroxyalkyl radical.

4. The process of claim 3 wherein at least about 1 mole of the dithiol and hydrogen sulfide components of the monomer system is employed per mole of olefin unsaturation present in the reaction zone.

5. The process of claim 3 wherein said polyolefin is a tri-terminal olefin having the general formula: R R'')xCH CH2)3 wherein R is a trivalent hydrocarbon radical having from one to 30 carbon atoms, R'' is a divalent radical having from one to 10 carbon atoms, and x varies from 0 to 1.

6. The process of claim 5 wherein R is a trivalent hydrocarbon radical having from 1 to 12 carbon atoms and x is 0.

7. The process of claim 6 wherein R'''' is an alkylene radical having from two to four carbon atoms and R'''''' is a C1 to C4 alkyl radical.

8. The process of claim 4 wherein said polyolefin is a trivinyl-cyclohexane, R'''' is an alkylene radical having from two to four carbon atoms and said acetylenic compound is methylacetylene.